1. a private feud in which the members of the family of a murdered person seek to avenge the murder by killing the slayer or one of the slayer's relatives, esp. such vengeance as once practiced in Corsica and parts of Italy.
2. any prolonged and bitter feud, rivalry, contention, or the like: a political vendetta.

I’m practically speechless. This episode was so amazing I’m at a loss for words almost. I have found only a few minor flaws, but I have never been so impressed. Here’s the review…
It starts in the Null Void where Ragnarok is being held in a special prison. He is escaping and when he is almost out, we finally see the Null guardians powers and that they almost have feelings; they seemed mad and disappointed when Ragnarok got away.
The scene switches to what seems to be a warehouse where Ben, Gwen, and Kevin are fighting the Forever Knights without much effort. Ben is Rath again-he seems to be getting popular. How clever when Gwen tells the Knights, ‘the Lady or the Tiger.’ I’m wondering if that is a reference to the short story. The team then defeats the Knights.
In the car on the way home, they actually talk about where Kevin lives! That topic has been floating around for a while now, and we finally got answers.
Apparently, that insight on information about Kevin was just a warm-up for seeing his house! Okay, so it was destroyed, but we actually went into Kevin’s home! We saw the outside of it AND then the inside?! I never thought this day would come, but holy crap that was definitely another warm-up for a bigger shock.
Kevin’s mom. She wasn’t shown for long, but we know her now. We know her voice, what she looks like, (kind of looks like Julie) and we saw how much Kevin cared. He was frantic worried about her. He thought she was in the house but thank goodness she wasn’t. Kevin couldn’t take it if he lost one more thing that was truly his in the world.
*Alright, so this is a note type thing. I completely knew what Kevin’s mom looked like way back in season one. I always thought about how she looked; short black hair with a broken aura about her. Then she comes up on this episode and exactly what I saw, was right. I’m a bigger fan than I thought.*
Anyway, it turns out that Kevin’s mom was lying for a long time about Kevin’s dad, and they have a conversation that we don’t see. Even though we don’t see it, we know that she told him about Ragnarok.
NOTE: In the picture of Kevin with his dad, Kevin IS SOOO CUTE!!!! I think he was about 5.
The scene then changes to Ben’s house, where Gwen and he are doing homework. Kevin shows up asking for answers about Ragnarok, but when Gwen and Ben don’t have any, Kevin tells them to stay out of the situation. Of course they don’t.
Now we are at Max’s motor home, where Ben and Gwen went to question Max about Ragnarok. Once that malevolent name is mentioned, Max freaks out a little and drops a cooking pan, changing his mood from light-hearted to enraged. Max then tells the story of his old plumber days with a young Plumber, and the encounter with Ragnarok.
We move on to a much lengthened scene of Max’s story. We finally see Kevin’s dad.
Kevin’s dad says the same smart remarks and one-liners just like Kevin does now. He looks like Superman a little bit with that small strand of hair on his forehead. He is funny in such a serious scene. Also, he has the dangerous energy absorption power that Kevin had a long time ago on the streets of New York City.
He jumps in front of Max when Ragnarok tries to kill Max. Max puts Ragnarok in the Null Void and goes to the young Plumber’s side. They show the darkest scene yet; Kevin’s dad dying in Max’s arms.
Back in real time when Max is done with the story, Ben asks what Kevin wants with Ragnarok. Max then reveals that his partner’s name was Devin Levin. Ragnarok is the monster that murdered Kevin’s dad.
The scene now turns to a storage unit, where Ragnarok is searching through garages. He is looking for the key, when Kevin shows up. Ragnarok calls Kevin an ‘osmosian’ which I’m guessing is an alien species that is made up of a mixture of many alien species, or a species that absorbs different elements. Kevin threatens to kill the murderer and they fight until Ben and Gwen show up. The two want to help Kevin, but he makes it clear once again that he wants them to stay out of it. At this point, it is one hundred percent clear that Kevin will kill Ragnarok. Gwen then helps find the key by searching Kevin’s subconscious. She ‘feels their connection.’ Gwevin!
Now we are back at Kevin’s house, where Gwen believes the key is. They find that the key is the picture of Kevin and his dad, and right then, Ragnarok appears and takes it. Ben turns into Diamondhead and they all fight. However, the murderer takes the picture frame and restores it to its form of a key, and puts it in his head to unlock his ship (gross). He tells Kevin that he is going to extinguish Kevin’s sun. Right then, I thought that he meant son as in baby boy, and I had a small freak out session. I thought, “He’s going to go to the future and kill Devlin?!” But he meant the planet.
Gwen then takes Ragnarok’s teleport signal, and they teleport to his ship. Kevin is now getting more angered and tells Ben to man up and they have a little tiff. When they split up, Ben mentions that he has never seen Kevin like this and that he is a different person. Gwen understands Kevin and says he is going through a lot. Also at this point she realizes that Kevin is serious about Ragnarok. Kevin now fools Gwen and Ben to go into an escape pod. Ben actually calls Kevin by his last name because things are getting more serious. I don’t ever recall Ben seriously calling Kevin ‘Levin’ before. He launches them back to earth. I thought Kevin would just trap them there; I didn’t think he would actually send them back.
Gwen: “Kevin is on his own.”
Ben: “Just like he planned it.”
Now Ragnarok is doing the sun sucking, and Kevin finds him. He starts destroying the equipment. Saving the Earth and avenging his dad. (I am freaking out here and totally don’t know what will happen or how Kevin will win, and I keep asking Kevin what he is going to do.) With a slip of the mouth, Ragnarok gives Kevin the information he needs to send the Sun energy back to the Sun and destroy part of the ship. The vortex is destabilized. Ragnarok is at his loss and has the nerve to ask Kevin to save him because Kevin’s dad would want it that way or some crap. Kevin just takes the key and lets him die, doing what he set out to do.
Back on Earth, Ben and Gwen see the ship explode and Gwen starts crying. Somehow (plot hole) Kevin is back on Earth. Gwen runs and hugs him and tells him how she was worried. When Ben asks about Ragnarok, Kevin simply says he didn’t make it.
Okay so overall this was the best episode of anything that I have ever watched hands down. The plot was amazing. The settings were ingenious being all over the place. The story was the most incredible part. It seemed like an hour long and we learned so much. It was the darkest episode of Ben 10 yet. I couldn’t give enough props to Dwayne McDuffie, and I am just beyond impressed.